1. Field of the Invention
The present invention pertains to a solar cell. More specifically, the present invention pertains to an electrode paste for a solar cell light-receiving surface being used in the manufacture of an electrode in a solar cell and a solar cell being obtained by using said paste.
2. Description of Related Art
In manufacturing an electrode for a solar cell, the electrode is formed at the side in which an anti-reflection film is formed. The generally used method for manufacturing the electrode is a method that spreads a paste containing glass frit, resin binder, thinner, and if necessary, additives on an anti-reflection film and [then] sinters it.
In order to raise the power generation characteristics in the solar cell, the characteristics of the electrode are important. For example, the power generation efficiency is raised by lowering the resistance value of the electrode. In order to achieve this purpose, various methods are proposed.
Silver particles are generally known as the electroconductive metal in the electrode of the solar cell. However, the relationship between the specific surface of the silver particles being used and the power generation characteristics is not deeply reviewed. In paragraph [0009] of Japanese Kokai Patent Application No. 2003-257243, “BET diameter” is defined as “the particle diameter attained, assuming that the particles have a spherical shape, based on the specific surface (m2/g) of the particles measured in the BET method.” According to said publication, the BET diameter of the silver particles being used is 0.10-0.50 μm. As application examples and comparative examples, silver powders with a BET diameter of 0.02-0.50 μm are presented.
Here, if the silver density=10.5 g/cm3=10.5×106 g/m3, the radius=R (μm)=R×10−6 m, and the specific surface=S (m2/g), the following equation is established.Weight of one silver particle=4π(R×10−6)2/S=(4π(R×10−6)3/3)×10.5×106 If this equation is solved with respect to S,S=3/(10.5×R).
Since the BET diameter is a diameter, the radius R is its half. Considering this, if the specific surface of the silver powder with a BET diameter of 0.02-0.50 μm, it [specific surface] is 1.1-28.6 m2/g.BET diameter of 0.02 μm=radius of 0.01 μm=specific surface of 28.6 m2/gBET diameter of 0.10 μm=radius of 0.05 μm=specific surface of 5.7 m2/gBET diameter of 0.50 μm=radius of 0.25 μm=specific surface of 1.1 m2/g